What is the best database of publications on plants?

Specifically, I am looking for examples of the use of in vitro cultures in agriculture and horticulture.

I just need a hint where to start, my options are limited to pubmed and books, but to these I have limited access and I do not want to waste money on a book, from which I will read 3 chapters, and the rest I will know from another source, so I am looking for the best source here, from you, because who if not you know best on the subject.

Inb4 google